// Written in 2014 by Andrew Poelstra <apoelstra@wpsoftware.net>
// SPDX-License-Identifier: CC0-1.0

//! Bitcoin blocks.
//!
//! A block is a bundle of transactions with a proof-of-work attached,
//! which commits to an earlier block to form the blockchain. This
//! module describes structures and functions needed to describe
//! these blocks and the blockchain.
//!

use crate::prelude::*;

use core::fmt;

use crate::util;
use crate::util::Error::{BlockBadTarget, BlockBadProofOfWork};
use crate::util::hash::bitcoin_merkle_root;
use crate::hashes::{Hash, HashEngine};
use crate::hash_types::{Wtxid, BlockHash, TxMerkleNode, WitnessMerkleNode, WitnessCommitment};
use crate::util::uint::Uint256;
use crate::consensus::encode::Encodable;
use crate::network::constants::Network;
use crate::blockdata::transaction::Transaction;
use crate::blockdata::constants::{max_target, WITNESS_SCALE_FACTOR};
use crate::blockdata::script;
use crate::VarInt;
use crate::internal_macros::impl_consensus_encoding;

/// Bitcoin block header.
///
/// Contains all the block's information except the actual transactions, but
/// including a root of a [merkle tree] commiting to all transactions in the block.
///
/// [merkle tree]: https://en.wikipedia.org/wiki/Merkle_tree
///
/// ### Bitcoin Core References
///
/// * [CBlockHeader definition](https://github.com/bitcoin/bitcoin/blob/345457b542b6a980ccfbc868af0970a6f91d1b82/src/primitives/block.h#L20)
#[derive(Copy, PartialEq, Eq, Clone, Debug, PartialOrd, Ord, Hash)]
#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
#[cfg_attr(feature = "serde", serde(crate = "actual_serde"))]
pub struct BlockHeader {
    /// Originally protocol version, but repurposed for soft-fork signaling.
    ///
    /// ### Relevant BIPs
    ///
    /// * [BIP9 - Version bits with timeout and delay](https://github.com/bitcoin/bips/blob/master/bip-0009.mediawiki) (current usage)
    /// * [BIP34 - Block v2, Height in Coinbase](https://github.com/bitcoin/bips/blob/master/bip-0034.mediawiki)
    pub version: i32,
    /// Reference to the previous block in the chain.
    pub prev_blockhash: BlockHash,
    /// The root hash of the merkle tree of transactions in the block.
    pub merkle_root: TxMerkleNode,
    /// The timestamp of the block, as claimed by the miner.
    pub time: u32,
    /// The target value below which the blockhash must lie, encoded as a
    /// a float (with well-defined rounding, of course).
    pub bits: u32,
    /// The nonce, selected to obtain a low enough blockhash.
    pub nonce: u32,
}

impl_consensus_encoding!(BlockHeader, version, prev_blockhash, merkle_root, time, bits, nonce);

impl BlockHeader {
    /// Returns the block hash.
    pub fn block_hash(&self) -> BlockHash {
        let mut engine = BlockHash::engine();
        self.consensus_encode(&mut engine).expect("engines don't error");
        BlockHash::from_engine(engine)
    }

    /// Computes the target [0, T] that a blockhash must land in to be valid.
    pub fn target(&self) -> Uint256 {
        Self::u256_from_compact_target(self.bits)
    }

    /// Computes the target value in [`Uint256`] format, from a compact representation.
    ///
    /// [`Uint256`]: ../../util/uint/struct.Uint256.html
    ///
    /// ```
    /// use bitcoin::blockdata::block::BlockHeader;
    ///
    /// assert_eq!(0x1d00ffff,
    ///     BlockHeader::compact_target_from_u256(
    ///         &BlockHeader::u256_from_compact_target(0x1d00ffff)
    ///     )
    /// );
    /// ```
    pub fn u256_from_compact_target(bits: u32) -> Uint256 {
        // This is a floating-point "compact" encoding originally used by
        // OpenSSL, which satoshi put into consensus code, so we're stuck
        // with it. The exponent needs to have 3 subtracted from it, hence
        // this goofy decoding code:
        let (mant, expt) = {
            let unshifted_expt = bits >> 24;
            if unshifted_expt <= 3 {
                ((bits & 0xFFFFFF) >> (8 * (3 - unshifted_expt as usize)), 0)
            } else {
                (bits & 0xFFFFFF, 8 * ((bits >> 24) - 3))
            }
        };

        // The mantissa is signed but may not be negative
        if mant > 0x7FFFFF {
            Default::default()
        } else {
            Uint256::from_u64(mant as u64).unwrap() << (expt as usize)
        }
    }

    /// Computes the target value in float format from Uint256 format.
    pub fn compact_target_from_u256(value: &Uint256) -> u32 {
        let mut size = (value.bits() + 7) / 8;
        let mut compact = if size <= 3 {
            (value.low_u64() << (8 * (3 - size))) as u32
        } else {
            let bn = *value >> (8 * (size - 3));
            bn.low_u32()
        };

        if (compact & 0x00800000) != 0 {
            compact >>= 8;
            size += 1;
        }

        compact | (size << 24) as u32
    }

    /// Computes the popular "difficulty" measure for mining.
    pub fn difficulty(&self, network: Network) -> u64 {
        (max_target(network) / self.target()).low_u64()
    }

    /// Checks that the proof-of-work for the block is valid, returning the block hash.
    pub fn validate_pow(&self, required_target: &Uint256) -> Result<BlockHash, util::Error> {
        let target = &self.target();
        if target != required_target {
            return Err(BlockBadTarget);
        }
        let block_hash = self.block_hash();
        let mut ret = [0u64; 4];
        util::endian::bytes_to_u64_slice_le(block_hash.as_inner(), &mut ret);
        let hash = &Uint256(ret);
        if hash <= target { Ok(block_hash) } else { Err(BlockBadProofOfWork) }
    }

    /// Returns the total work of the block.
    pub fn work(&self) -> Uint256 {
        // 2**256 / (target + 1) == ~target / (target+1) + 1    (eqn shamelessly stolen from bitcoind)
        let mut ret = !self.target();
        let mut ret1 = self.target();
        ret1.increment();
        ret = ret / ret1;
        ret.increment();
        ret
    }
}

/// Bitcoin block.
///
/// A collection of transactions with an attached proof of work.
///
/// See [Bitcoin Wiki: Block][wiki-block] for more information.
///
/// [wiki-block]: https://en.bitcoin.it/wiki/Block
///
/// ### Bitcoin Core References
///
/// * [CBlock definition](https://github.com/bitcoin/bitcoin/blob/345457b542b6a980ccfbc868af0970a6f91d1b82/src/primitives/block.h#L62)
#[derive(PartialEq, Eq, Clone, Debug)]
#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
#[cfg_attr(feature = "serde", serde(crate = "actual_serde"))]
pub struct Block {
    /// The block header
    pub header: BlockHeader,
    /// List of transactions contained in the block
    pub txdata: Vec<Transaction>
}

impl_consensus_encoding!(Block, header, txdata);

impl Block {
    /// Returns the block hash.
    pub fn block_hash(&self) -> BlockHash {
        self.header.block_hash()
    }

    /// check if merkle root of header matches merkle root of the transaction list
    pub fn check_merkle_root(&self) -> bool {
        match self.compute_merkle_root() {
            Some(merkle_root) => self.header.merkle_root == merkle_root,
            None => false,
        }
    }

    /// Checks if witness commitment in coinbase matches the transaction list.
    pub fn check_witness_commitment(&self) -> bool {
        const MAGIC: [u8; 6] = [0x6a, 0x24, 0xaa, 0x21, 0xa9, 0xed];
        // Witness commitment is optional if there are no transactions using SegWit in the block.
        if self.txdata.iter().all(|t| t.input.iter().all(|i| i.witness.is_empty())) {
            return true;
        }

        if self.txdata.is_empty() {
            return false;
        }

        let coinbase = &self.txdata[0];
        if !coinbase.is_coin_base() {
            return false;
        }

        // Commitment is in the last output that starts with magic bytes.
        if let Some(pos) = coinbase.output.iter()
            .rposition(|o| o.script_pubkey.len () >= 38 && o.script_pubkey[0..6] ==  MAGIC)
        {
            let commitment = WitnessCommitment::from_slice(&coinbase.output[pos].script_pubkey.as_bytes()[6..38]).unwrap();
            // Witness reserved value is in coinbase input witness.
            let witness_vec: Vec<_> = coinbase.input[0].witness.iter().collect();
            if witness_vec.len() == 1 && witness_vec[0].len() == 32 {
                if let Some(witness_root) = self.witness_root() {
                    return commitment == Self::compute_witness_commitment(&witness_root, witness_vec[0]);
                }
            }
        }

        false
    }

    /// Computes the transaction merkle root.
    pub fn compute_merkle_root(&self) -> Option<TxMerkleNode> {
        let hashes = self.txdata.iter().map(|obj| obj.txid().as_hash());
        bitcoin_merkle_root(hashes).map(|h| h.into())
    }

    /// Calculate the transaction merkle root.
    #[deprecated(since = "0.28.0", note = "Please use `block::compute_merkle_root` instead.")]
    pub fn merkle_root(&self) -> Option<TxMerkleNode> {
        self.compute_merkle_root()
    }

    /// Computes the witness commitment for the block's transaction list.
    pub fn compute_witness_commitment(witness_root: &WitnessMerkleNode, witness_reserved_value: &[u8]) -> WitnessCommitment {
        let mut encoder = WitnessCommitment::engine();
        witness_root.consensus_encode(&mut encoder).expect("engines don't error");
        encoder.input(witness_reserved_value);
        WitnessCommitment::from_engine(encoder)
    }

    /// Computes the merkle root of transactions hashed for witness.
    pub fn witness_root(&self) -> Option<WitnessMerkleNode> {
        let hashes = self.txdata.iter().enumerate().map(|(i, t)| {
            if i == 0 {
                // Replace the first hash with zeroes.
                Wtxid::all_zeros().as_hash()
            } else {
                t.wtxid().as_hash()
            }
        });
        bitcoin_merkle_root(hashes).map(|h| h.into())
    }

    /// base_size == size of header + size of encoded transaction count.
    fn base_size(&self) -> usize {
        80 + VarInt(self.txdata.len() as u64).len()
    }

    /// Returns the size of the block.
    #[deprecated(since = "0.28.0", note = "Please use `block::size` instead.")]
    pub fn get_size(&self) -> usize {
        self.size()
    }

    /// Returns the size of the block.
    ///
    /// size == size of header + size of encoded transaction count + total size of transactions.
    pub fn size(&self) -> usize {
        let txs_size: usize = self.txdata.iter().map(Transaction::size).sum();
        self.base_size() + txs_size
    }

    /// Returns the strippedsize of the block.
    #[deprecated(since = "0.28.0", note = "Please use `transaction::strippedsize` instead.")]
    pub fn get_strippedsize(&self) -> usize {
        self.strippedsize()
    }

    /// Returns the strippedsize of the block.
    pub fn strippedsize(&self) -> usize {
        let txs_size: usize = self.txdata.iter().map(Transaction::strippedsize).sum();
        self.base_size() + txs_size
    }

    /// Returns the weight of the block.
    #[deprecated(since = "0.28.0", note = "Please use `transaction::weight` instead.")]
    pub fn get_weight(&self) -> usize {
        self.weight()
    }

    /// Returns the weight of the block.
    pub fn weight(&self) -> usize {
        let base_weight = WITNESS_SCALE_FACTOR * self.base_size();
        let txs_weight: usize = self.txdata.iter().map(Transaction::weight).sum();
        base_weight + txs_weight
    }

    /// Returns the coinbase transaction, if one is present.
    pub fn coinbase(&self) -> Option<&Transaction> {
        self.txdata.first()
    }

    /// Returns the block height, as encoded in the coinbase transaction according to BIP34.
    pub fn bip34_block_height(&self) -> Result<u64, Bip34Error> {
        // Citing the spec:
        // Add height as the first item in the coinbase transaction's scriptSig,
        // and increase block version to 2. The format of the height is
        // "serialized CScript" -- first byte is number of bytes in the number
        // (will be 0x03 on main net for the next 150 or so years with 2^23-1
        // blocks), following bytes are little-endian representation of the
        // number (including a sign bit). Height is the height of the mined
        // block in the block chain, where the genesis block is height zero (0).

        if self.header.version < 2 {
            return Err(Bip34Error::Unsupported);
        }

        let cb = self.coinbase().ok_or(Bip34Error::NotPresent)?;
        let input = cb.input.first().ok_or(Bip34Error::NotPresent)?;
        let push = input.script_sig.instructions_minimal().next().ok_or(Bip34Error::NotPresent)?;
        match push.map_err(|_| Bip34Error::NotPresent)? {
            script::Instruction::PushBytes(b) if b.len() <= 8 => {
                // Expand the push to exactly 8 bytes (LE).
                let mut full = [0; 8];
                full[0..b.len()].copy_from_slice(b);
                Ok(util::endian::slice_to_u64_le(&full))
            }
            script::Instruction::PushBytes(b) if b.len() > 8 => {
                Err(Bip34Error::UnexpectedPush(b.to_vec()))
            }
            _ => Err(Bip34Error::NotPresent),
        }
    }
}

/// An error when looking up a BIP34 block height.
#[derive(Debug, Clone, PartialEq, Eq)]
#[non_exhaustive]
pub enum Bip34Error {
    /// The block does not support BIP34 yet.
    Unsupported,
    /// No push was present where the BIP34 push was expected.
    NotPresent,
    /// The BIP34 push was larger than 8 bytes.
    UnexpectedPush(Vec<u8>),
}

impl fmt::Display for Bip34Error {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            Bip34Error::Unsupported => write!(f, "block doesn't support BIP34"),
            Bip34Error::NotPresent => write!(f, "BIP34 push not present in block's coinbase"),
            Bip34Error::UnexpectedPush(ref p) => {
                write!(f, "unexpected byte push of > 8 bytes: {:?}", p)
            }
        }
    }
}

#[cfg(feature = "std")]
#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
impl std::error::Error for Bip34Error {
    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
        use self::Bip34Error::*;

        match self {
            Unsupported | NotPresent | UnexpectedPush(_) => None,
        }
    }
}

#[cfg(test)]
mod tests {
    use crate::hashes::hex::FromHex;

    use crate::blockdata::block::{Block, BlockHeader};
    use crate::consensus::encode::{deserialize, serialize};
    use crate::util::uint::Uint256;
    use crate::util::Error::{BlockBadTarget, BlockBadProofOfWork};
    use crate::network::constants::Network;

    #[test]
    fn test_coinbase_and_bip34() {
        // testnet block 100,000
        let block_hex = "0200000035ab154183570282ce9afc0b494c9fc6a3cfea05aa8c1add2ecc56490000000038ba3d78e4500a5a7570dbe61960398add4410d278b21cd9708e6d9743f374d544fc055227f1001c29c1ea3b0101000000010000000000000000000000000000000000000000000000000000000000000000ffffffff3703a08601000427f1001c046a510100522cfabe6d6d0000000000000000000068692066726f6d20706f6f6c7365727665726aac1eeeed88ffffffff0100f2052a010000001976a914912e2b234f941f30b18afbb4fa46171214bf66c888ac00000000";
        let block: Block = deserialize(&Vec::<u8>::from_hex(block_hex).unwrap()).unwrap();

        let cb_txid = "d574f343976d8e70d91cb278d21044dd8a396019e6db70755a0a50e4783dba38";
        assert_eq!(block.coinbase().unwrap().txid().to_string(), cb_txid);

        assert_eq!(block.bip34_block_height(), Ok(100_000));


        // block with 9-byte bip34 push
        let bad_hex = "0200000035ab154183570282ce9afc0b494c9fc6a3cfea05aa8c1add2ecc56490000000038ba3d78e4500a5a7570dbe61960398add4410d278b21cd9708e6d9743f374d544fc055227f1001c29c1ea3b0101000000010000000000000000000000000000000000000000000000000000000000000000ffffffff3d09a08601112233445566000427f1001c046a510100522cfabe6d6d0000000000000000000068692066726f6d20706f6f6c7365727665726aac1eeeed88ffffffff0100f2052a010000001976a914912e2b234f941f30b18afbb4fa46171214bf66c888ac00000000";
        let bad: Block = deserialize(&Vec::<u8>::from_hex(bad_hex).unwrap()).unwrap();

        let push = Vec::<u8>::from_hex("a08601112233445566").unwrap();
        assert_eq!(bad.bip34_block_height(), Err(super::Bip34Error::UnexpectedPush(push)));
    }

    #[test]
    fn block_test() {
        // Mainnet block 00000000b0c5a240b2a61d2e75692224efd4cbecdf6eaf4cc2cf477ca7c270e7
        let some_block = Vec::from_hex("010000004ddccd549d28f385ab457e98d1b11ce80bfea2c5ab93015ade4973e400000000bf4473e53794beae34e64fccc471dace6ae544180816f89591894e0f417a914cd74d6e49ffff001d323b3a7b0201000000010000000000000000000000000000000000000000000000000000000000000000ffffffff0804ffff001d026e04ffffffff0100f2052a0100000043410446ef0102d1ec5240f0d061a4246c1bdef63fc3dbab7733052fbbf0ecd8f41fc26bf049ebb4f9527f374280259e7cfa99c48b0e3f39c51347a19a5819651503a5ac00000000010000000321f75f3139a013f50f315b23b0c9a2b6eac31e2bec98e5891c924664889942260000000049483045022100cb2c6b346a978ab8c61b18b5e9397755cbd17d6eb2fe0083ef32e067fa6c785a02206ce44e613f31d9a6b0517e46f3db1576e9812cc98d159bfdaf759a5014081b5c01ffffffff79cda0945903627c3da1f85fc95d0b8ee3e76ae0cfdc9a65d09744b1f8fc85430000000049483045022047957cdd957cfd0becd642f6b84d82f49b6cb4c51a91f49246908af7c3cfdf4a022100e96b46621f1bffcf5ea5982f88cef651e9354f5791602369bf5a82a6cd61a62501fffffffffe09f5fe3ffbf5ee97a54eb5e5069e9da6b4856ee86fc52938c2f979b0f38e82000000004847304402204165be9a4cbab8049e1af9723b96199bfd3e85f44c6b4c0177e3962686b26073022028f638da23fc003760861ad481ead4099312c60030d4cb57820ce4d33812a5ce01ffffffff01009d966b01000000434104ea1feff861b51fe3f5f8a3b12d0f4712db80e919548a80839fc47c6a21e66d957e9c5d8cd108c7a2d2324bad71f9904ac0ae7336507d785b17a2c115e427a32fac00000000").unwrap();
        let cutoff_block = Vec::from_hex("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").unwrap();

        let prevhash = Vec::from_hex("4ddccd549d28f385ab457e98d1b11ce80bfea2c5ab93015ade4973e400000000").unwrap();
        let merkle = Vec::from_hex("bf4473e53794beae34e64fccc471dace6ae544180816f89591894e0f417a914c").unwrap();
        let work = Uint256([0x100010001u64, 0, 0, 0]);

        let decode: Result<Block, _> = deserialize(&some_block);
        let bad_decode: Result<Block, _> = deserialize(&cutoff_block);

        assert!(decode.is_ok());
        assert!(bad_decode.is_err());
        let real_decode = decode.unwrap();
        assert_eq!(real_decode.header.version, 1);
        assert_eq!(serialize(&real_decode.header.prev_blockhash), prevhash);
        assert_eq!(real_decode.header.merkle_root, real_decode.compute_merkle_root().unwrap());
        assert_eq!(serialize(&real_decode.header.merkle_root), merkle);
        assert_eq!(real_decode.header.time, 1231965655);
        assert_eq!(real_decode.header.bits, 486604799);
        assert_eq!(real_decode.header.nonce, 2067413810);
        assert_eq!(real_decode.header.work(), work);
        assert_eq!(real_decode.header.validate_pow(&real_decode.header.target()).unwrap(), real_decode.block_hash());
        assert_eq!(real_decode.header.difficulty(Network::Bitcoin), 1);
        // [test] TODO: check the transaction data

        assert_eq!(real_decode.size(), some_block.len());
        assert_eq!(real_decode.strippedsize(), some_block.len());
        assert_eq!(real_decode.weight(), some_block.len() * 4);

        // should be also ok for a non-witness block as commitment is optional in that case
        assert!(real_decode.check_witness_commitment());

        assert_eq!(serialize(&real_decode), some_block);
    }

    // Check testnet block 000000000000045e0b1660b6445b5e5c5ab63c9a4f956be7e1e69be04fa4497b
    #[test]
    fn segwit_block_test() {
        let segwit_block = include_bytes!("../../test_data/testnet_block_000000000000045e0b1660b6445b5e5c5ab63c9a4f956be7e1e69be04fa4497b.raw").to_vec();

        let decode: Result<Block, _> = deserialize(&segwit_block);

        let prevhash = Vec::from_hex("2aa2f2ca794ccbd40c16e2f3333f6b8b683f9e7179b2c4d74906000000000000").unwrap();
        let merkle = Vec::from_hex("10bc26e70a2f672ad420a6153dd0c28b40a6002c55531bfc99bf8994a8e8f67e").unwrap();
        let work = Uint256([0x257c3becdacc64u64, 0, 0, 0]);

        assert!(decode.is_ok());
        let real_decode = decode.unwrap();
        assert_eq!(real_decode.header.version, 0x20000000);  // VERSIONBITS but no bits set
        assert_eq!(serialize(&real_decode.header.prev_blockhash), prevhash);
        assert_eq!(serialize(&real_decode.header.merkle_root), merkle);
        assert_eq!(real_decode.header.merkle_root, real_decode.compute_merkle_root().unwrap());
        assert_eq!(real_decode.header.time, 1472004949);
        assert_eq!(real_decode.header.bits, 0x1a06d450);
        assert_eq!(real_decode.header.nonce, 1879759182);
        assert_eq!(real_decode.header.work(), work);
        assert_eq!(real_decode.header.validate_pow(&real_decode.header.target()).unwrap(), real_decode.block_hash());
        assert_eq!(real_decode.header.difficulty(Network::Testnet), 2456598);
        // [test] TODO: check the transaction data

        assert_eq!(real_decode.size(), segwit_block.len());
        assert_eq!(real_decode.strippedsize(), 4283);
        assert_eq!(real_decode.weight(), 17168);

        assert!(real_decode.check_witness_commitment());

        assert_eq!(serialize(&real_decode), segwit_block);
    }

    #[test]
    fn block_version_test() {
        let block = Vec::from_hex("ffffff7f0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000").unwrap();
        let decode: Result<Block, _> = deserialize(&block);
        assert!(decode.is_ok());
        let real_decode = decode.unwrap();
        assert_eq!(real_decode.header.version, 2147483647);

        let block2 = Vec::from_hex("000000800000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000").unwrap();
        let decode2: Result<Block, _> = deserialize(&block2);
        assert!(decode2.is_ok());
        let real_decode2 = decode2.unwrap();
        assert_eq!(real_decode2.header.version, -2147483648);
    }

    #[test]
    fn validate_pow_test() {
        let some_header = Vec::from_hex("010000004ddccd549d28f385ab457e98d1b11ce80bfea2c5ab93015ade4973e400000000bf4473e53794beae34e64fccc471dace6ae544180816f89591894e0f417a914cd74d6e49ffff001d323b3a7b").unwrap();
        let some_header: BlockHeader = deserialize(&some_header).expect("Can't deserialize correct block header");
        assert_eq!(some_header.validate_pow(&some_header.target()).unwrap(), some_header.block_hash());

        // test with zero target
        match some_header.validate_pow(&Uint256::default()) {
            Err(BlockBadTarget) => (),
            _ => panic!("unexpected result from validate_pow"),
        }

        // test with modified header
        let mut invalid_header: BlockHeader = some_header;
        invalid_header.version += 1;
        match invalid_header.validate_pow(&invalid_header.target()) {
            Err(BlockBadProofOfWork) => (),
            _ => panic!("unexpected result from validate_pow"),
        }
    }

    #[test]
    fn compact_roundrtip_test() {
        let some_header = Vec::from_hex("010000004ddccd549d28f385ab457e98d1b11ce80bfea2c5ab93015ade4973e400000000bf4473e53794beae34e64fccc471dace6ae544180816f89591894e0f417a914cd74d6e49ffff001d323b3a7b").unwrap();

        let header: BlockHeader = deserialize(&some_header).expect("Can't deserialize correct block header");

        assert_eq!(header.bits, BlockHeader::compact_target_from_u256(&header.target()));
    }
}

#[cfg(bench)]
mod benches {
    use super::Block;
    use crate::EmptyWrite;
    use crate::consensus::{deserialize, Encodable, Decodable};
    use test::{black_box, Bencher};

    #[bench]
    pub fn bench_stream_reader(bh: &mut Bencher) {
        let big_block = include_bytes!("../../test_data/mainnet_block_000000000000000000000c835b2adcaedc20fdf6ee440009c249452c726dafae.raw");
        assert_eq!(big_block.len(), 1_381_836);
        let big_block = black_box(big_block);

        bh.iter(|| {
            let mut reader = &big_block[..];
            let block = Block::consensus_decode(&mut reader).unwrap();
            black_box(&block);
        });
    }

    #[bench]
    pub fn bench_block_serialize(bh: &mut Bencher) {
        let raw_block = include_bytes!("../../test_data/mainnet_block_000000000000000000000c835b2adcaedc20fdf6ee440009c249452c726dafae.raw");

        let block: Block = deserialize(&raw_block[..]).unwrap();

        let mut data = Vec::with_capacity(raw_block.len());

        bh.iter(|| {
            let result = block.consensus_encode(&mut data);
            black_box(&result);
            data.clear();
        });
    }

    #[bench]
    pub fn bench_block_serialize_logic(bh: &mut Bencher) {
        let raw_block = include_bytes!("../../test_data/mainnet_block_000000000000000000000c835b2adcaedc20fdf6ee440009c249452c726dafae.raw");

        let block: Block = deserialize(&raw_block[..]).unwrap();

        bh.iter(|| {
            let size = block.consensus_encode(&mut EmptyWrite);
            black_box(&size);
        });
    }

    #[bench]
    pub fn bench_block_deserialize(bh: &mut Bencher) {
        let raw_block = include_bytes!("../../test_data/mainnet_block_000000000000000000000c835b2adcaedc20fdf6ee440009c249452c726dafae.raw");

        bh.iter(|| {
            let block: Block = deserialize(&raw_block[..]).unwrap();
            black_box(&block);
        });
    }
}